(function(doc, win) {
			var docEle = doc.documentElement,
				dpr = Math.min(win.devicePixelRatio, 3),
				scale = 1 / dpr,
				resizeEvent = 'orientationchange' in window ? 'orientationchange' : 'resize';
			var metaEle = doc.createElement('meta');
			metaEle.name = 'viewport';
			metaEle.content = 'initial-scale=' + scale + ',maximum-scale=' + scale;
			docEle.firstElementChild.appendChild(metaEle);
			var recalCulate = function() {
				var width = docEle.clientWidth;
				docEle.style.fontSize = 10 * (width / 750) + 'px';
			};
			recalCulate();
			if (!doc.addEventListener) return;
			win.addEventListener(resizeEvent, recalCulate, false);
		})(document, window);